Boiler Efficiency - Direct Method
Direct (input-output) efficiency: useful heat in steam vs. fuel energy. Fast and accurate when steam flow and fuel flow are metered.
Boiler efficiency
76.67%
Formula, assumptions, and limits
Modern oil-fired marine boilers achieve 85–92 % direct efficiency; exhaust-gas economisers displaced by main-engine waste heat can push composite-plant efficiency to 92–95 %.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| Steam produced | kg/h | steam meter | |
| Steam enthalpy | kJ/kg | steam tables | |
| Feedwater enthalpy | kJ/kg | feedwater tank | |
| Fuel consumed | kg/h | flow meter | |
| Lower calorific value | kJ/kg | ISO 8217 | |
| Direct efficiency | - | result |